<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
        html,
        body {
            margin: 0;
            padding: 0;
        }

        body {
            width: 100vw;
            height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
            background: #000;
        }

        .card {
            position: relative;
            width: 220px;
            height: 320px;
            background: mediumturquoise;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 25px;
            font-weight: bold;
            border-radius: 15px;
            cursor: pointer;
        }

        .card::before,
        .card::after {
            position: absolute;
            content: "";
            width: 20%;
            height: 20%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 25px;
            font-weight: bold;
            background-color: lightblue;
            transition: all 0.5s;
        }

        .card::before {
            top: 0;
            right: 0;
            border-radius: 0 15px 0 100%;
        }

        .card::after {
            bottom: 0;
            left: 0;
            border-radius: 0 100% 0 15px;
        }

        .card:hover::before,
        .card:hover:after {
            width: 100%;
            height: 100%;
            border-radius: 15px;
            transition: all 0.5s;
        }

        .card:hover:after {
            content: "HELLO";
        }
    </style>
</head>

<body> /* From Uiverse.io by eslam-hany */ <div class="card">HOVER</div>
</body>

</html>